Method for producing an electrochromic device

ABSTRACT

Disclosed is a method for producing an electrochromic device providing an opening in the surface of each of the two electrically conductive substrates of the cell, not in the end surface of the opposed substrates, to fill the inside of the hollow cell with an electrolyte or the precursor thereof by injecting through the injection port, to seal temporarily the injection port with a material which can be deformably inserted into the port and to seal secondarily the temporarily sealed port by applying thereon only an adhesive or a sheet-like member over the adhesive.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for producing an electrochromicdevice.

2. Prior Art

An electrochromic device is generally produced by sealing the periphery,except for a portion thereof, of a pair of electrically conductivesubstrates, at least one of which is transparent, placed In aspaced-apart opposing relationship so as to assemble a cell having aninjection port formed by the unsealed portion and filling the innerspace of the cell by charging through the port an electrolyte or theprecursor thereof in a vacuum. The injection port of the cell is thensealed by filling and curing therein a photo-setting or thermosettingacrylic resin or epoxy resin adhesive.

However, such a method for sealing or closing the port requires a stepof removing the electrolyte adhered around the injection port prior tofilling the adhesive. If the electrolyte is not removed completely, theadhesive can not seal the port sufficiently. Furthermore, the abovesealing method fails to obtain satisfactory sealing strength due to aninsufficient cure of the adhesive caused by the contact thereof with theelectrolyte.

Japanese Laid-Open Patent Publication Nos. 2-114237 and 6-250230disclose a two-step sealing method to solve the foregoing problems.

Japanese Laid-Open Patent Publication No. 2-114237 discloses a methodwhich comprises a primary sealing and a secondary sealing. In thismethod, first of all, there is prepared a cell having an opening formedin a selected portion of the peripheral edges of a pair of substrates inopposing relation. After an electrolyte is charged through the opening,the primary sealing is conducted by coating an epoxy resin adhesive tothe opening while an external pressure is vertically applied to thesubstrates followed by releasing the pressure to allow the sealant toenter into the inside of the opening and cure therein. After a certainperiod of time, the secondary sealing is carried out by coating an epoxyresin adhesive on the peripheral edges of the substrate including theprimary sealed portion and allowing the adhesive to cure it self

This method is recognized as being applicable to the production for aelectrochromic device of a relatively small size. However, the method isnot always suitable for the production for an electrochromic device of arelatively large size because the primary sealing requires the processof applying an external pressure onto the cell. Furthermore, thistwo-step sealing method is mainly focused on the injection port(opening) provided on the end surface of the cell. Therefore, when thismethod is employed for producing the large electrochromic device, theremay arise a risk that the adhesive would peel off due to the stressapplied to the sealing portion upon transportation of the device eventhough the sealing is completed in a satisfactory manner.

Japanese Laid-Open Publication No. 6-250230 proposes a method by whichan electrolyte injection port is sealed vaith a radiation cure typeadhesive and then sealed with an epoxy resin adhesive so as to beoverlapped with the former adhesive. However, with this method the aboverisk can not be removed because it also attempts to solve the aboveproblem by providing the electrolyte injection port in the end surfaceof the cell.

An object of the invention is to provide a method for producing anelectrochromic device of which sealing portion of the electrolyteinjection port is free from the peel off of the adhesive by providingthe electrolyte injection port in one of the two opposing substrates,not in the peripheral edge of the cell, even upon the production of alarge size electrochromic device on which stress would possibly appliedduring the transportation of the device,

Another object of the invention is to provide a method for producing anelectrochromic device. The method can avoid completely the contactbetween an electrolyte and an adhesive to be used for sealing theelectrolyte injection port and thus is also free from a risk that thecuring reaction of the adhesive is hindered.

SUMMARY OF THE INVENTION

According to the invention, there is provided a method for producing anelectrochromic device which comprises:

(a) a step of assembling a hollow cell constituting an electrochromicdevice by opposing two electrically conductive substrates, at least oneof which is transparent and either of which is provided with aninjection port for an electrolyte, in a spaced-apart relationship witheach other and sealing together the entire peripheral edges of theopposed substrates;

(b) a step of filling the inside of the hollow cell with an electrolyteor the precursor thereof by injecting through the injection port;

(c) a step of sealing temporarily the injection port with a materialwhich can be deformably inserted into the injection port; and

(d) a step of sealing secondarily the temporarily sealed port byapplying thereon only an adhesive or a plate-like member over theadhesive.

DETAILED DESCRIPTION OF THE INVENTION

An electrically conductive substrate used for the inventive method meansliterally a substrate functioning as an electrode. The electricallyconductive substrate may be that of which substrate itself iselectrically conductive or that of which is not electrically conductivebut has an electrode layer disposed on the surface contacting the layerof an electrolyte.

Such an electrically conductive substrate may be iron, copper, silver,aluminum, tin, lead, gold and zinc and,alloys thereof. Thenonelectrically conductive substrate may be any type of substrate aslong as it has a smooth surface. Specific examples are substrates madeof a material such as plastics (synthetic resin), glass, wood and stone.

The electrochromic device produced by the invention includes a pair ofsuch electrically conductive substrates one of which is necessarilytransparent. Such an electrically conductive transparent substrate maybe produced by laminating an electrode layer on a transparent substrate.The transparent substrate may be colored or colorless glass as well ascolored or colorless plastic (synthetic resin). Eligible plastics forthis purpose are polyethylene terephthalate, polyamide, polysultone,polyether sulfone, polyether etherketone, polyphenylene sulfide,polycarbonate, polyimide, polymethyl methacrylate and polystyrene.

The term “transparent” used herein designates optical transmissionranging from 10 to 100%. The substrate used for the invention may beflat or curved and may be deformable by stress as long as it has asmooth surface at room temperature.

It is preferred that the electrode layer to be laminated on thenon-electrically conductive substrate Is transparent. It is requisitethat at least the electrode layer to be laminated on the transparentsubstrate is transparent. Eligible for the electrode layer are a thinfilm of metal such as gold, silver, chrome, copper and tungsten or ametal oxide such as ITO (In₂O₃—SnO₂), tin oxide, silver oxide, zincoxide and vanadium oxide.

The thickness of the electrode is selective within the range of usually10 to 1,000, preferably 50 to 300 nm. The surface resistance of theelectrode may be selected suitably but usually in the range of 0.5-500,preferably 1-50 Ω/sq.

No particular limitation is imposed on the formation method of theelectrode layer. Any suitable conventional methods may be selecteddepending upon the metal and metal oxide constituting the electrode. Ingeneral, the formation of the electrode layer is carried out by vacuumevaporation, ion plating, sputtering and a sdoel method In any case, theformation of the electrode should be conducted while maintaining thetemperature of the substrate within the range of 100-350° C.

The electrode layer may partially provided with an opaqueelectrode-activator in order for the purpose of impartingoxidation-reduction capability and increasing electric double layercapacitance. In this case, if it is necessary to maintain thetransparency of the electrode, the optical transmission of the wholeelectrode is kept within the range of 10-100%.

Electrode activators eligible for the purpose of the invention include ametal such as copper, silver, gold, platinum, iron, tungsten, titaniumand lithium, an organic material having oxidation-reduction capabilitysuch as polyaniline, polytiophen, polypyrrole and phthalocyanine, acarbon material such as active carbon and graphite and a metal oxidesuch as V₂O₅, WO₃, MnO₂, NiO and Ir₂O₃ and mixtures thereof. Theseelectrode activators may be integrated to the electrode with a binderresin.

The opaque electrode activator may be applied onto an electrode byforming over an ITO transparent electrode a composition comprising anactive carbon fiber, graphite and an acrylic resin in the shape ofstripes or by forming on a thin-film of gold (Au) a compositioncomprising V₂O₅), acetylene black and butyl rubber in a meshed pattern.

One of the two electrically conductive substrates used for the inventivehas in the surface an opening of 0.5-10, preferably 2-6 mm φ whichopening is used as an injection port for an electrolyte.

The cell for the electrochromic device according to the invention isproduced by opposing the two electrically conductive substrates, one ofwhich is transparent, in a spaced-apart relation and sealing the wholeperipheral edges of the opposed substrates. If the electricallyconductive substrate is one obtained by laminating an electrode layerthereon, the electrode layer is placed to face the inside of the cell.The space between the opposed substrates is within the range of usually30-1,000, preferably 200-500 μm.

Needless to mention, an electrochromic device contains an electrochromicmaterial. Such an electrochromic material may be mixed in an electrolytelayer or formed into the electrochromic layer separately from theelectrolyte layer The electrochromic layer may be arranged anywhere theinside of the cell. In general, prior to the assembly of the cell, theelectrochromic layer may be arranged on at least one or both of theelectrode layers on the electrically conductive substrates. When theelectrochromic material is mixed into the electrolyte layer, there maybe employed a method in which to inject the mixture of an electrolyte orthe precursor thereof and the electrochromic material into the cell.

The electrochromic material may be exemplified by substances colored,bleached or discolored by electrochemical oxidation or reduction such asMO₂O₃, Ir₂O₃, NiO, V₂O₅, WO₃, biologen, polythiophene, polyanilinespolypyrrole, metal phthalocyanine and ferrocene.

The electrochromic layer may be formed solely from the electrochromicmaterial or may be formed from the electrochromic material and thematrix component thereof, the former being preferred The electrochromiclayer has a thickness In the range of usually 10 nm-1 μm, preferably50-800 nm

There may be employed any conventional method for forming theelectrochromic layer such as vacuum evaporation, ion-plating,sputtering, electrolytic polymerization, dip coating and spin coating.

No particular limitation imposed on a sealant used for sealing theperipheral edges of the opposed electrically conductive substrates aslong as it can seal up the device so as to isolate the interior thereoffrom its surroundings and so as to prevent a component such as moisture,oxygen and carbon monoxide adversely effecting the performances of thedevice from permeating into the interior of the device. Therefore,eligible sealants are exemplified by synthetic resins includingpolyester such as polyethylene terephtalate, polyamide, polysulfone,polyether sulfone, polyether etherketone, polyphenylene sulfide,polycarbonate, polyimide, polymethyl methacrylate, polystyrene,tricellulose acetate, polymethylpentene, polysiloxane, polyethylene,polypropylene, polycellulose acetate, phenolic resin, urea resin, epoxyresin, polyvinyl acetate, polyvinyl acetal, polyvinyl alcohol, acrylicand methacrylic esters and, cyanoacrylate; natural rubbers; andsynthetic rubbers such as isoprene rubber, butadlene rubber,styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber,chloropylene rubber, chlorosulfonated polyethylene, nitrile rubber,urethane rubber, polysulfide rubber, acrylic rubber, epichlorohydrinrubber, silicone rubber, fluorine rubber and hydrogenated nitrilerubber.

Alternatively, hardening resins are also eligible for the sealant. Thereis no particular limitation to the hardening resins and thus varioushardening type of resins are eligible such as those cured by heat andelectromagnetic ray. Eligible hardening resins are phenolic resin, urearesin, epoxy resin, polyvinyl acetate, polyvinyl acetal, polyvinylalcohol, acrylic and methacrylic esters, cyanoacrylate and polyamide.These may be used singular or in combination. Further alternatively,these resins may be modified by adding fillers. Among these,particularly preferred are an epoxy resin and an acrylic-modified epoxyresin Preferred acrylic-modified epoxy resins are those containing0.01-0.3 mol of acrylic residue per mol of epoxy residue, preferably0.05-0.2 mol of acrylic residue per mol of epoxy residue.

When the peripheral edges of the opposed electrically conductivesubstrates are sealed, it is preferred to use a spacer for adjusting thewidth of the space between the substrates. The spacer needs to benon-electrically conductive but may have sheet-, sphere-, fiber- or bar-like shape.

There may be employed any suitable method for sealing the electricallyconductive substrates such as the following methods:

(1) Inserting the sealing material having been processed and formed inconformity with the shape of the electrically conductive substratestherebetween;

(2) Coating the above-mentioned hardening resin paste in a desired shapeover the surface of the substrate using a known printing method;

(3) Coating the sealant over the surface of the substrate; and

(4) Forming the sealant discharged from a nozzle into a suitable patternon the substrate by moving the nozzle.

Among these, particularly preferred is method (4).

The sealant may be applied to either one or both of the substrates.

When the hardening resin is applied to the substrate, It is hardenedafter the substrates are laminated. Needless to mention, the hardeningis effected depending on the resin used.

If a thermal-hardening resin is used, there may be used such a resinhardening at room temperature. If a thermal-hardening resin requiringheat to be hardened is used, it is selected from the resins which hardenat a temperature ranging from room temperature to 150° C., preferablyfrom room temperature to 100° C. The period of time required forhardening is selected to an extent that electrochromic characteristicsare not adversely effected, preferably from the range within 24 hours,more preferably from the range within one hour.

If a photo-hardening resin is employed, there may be used various typesof light sources as long as they initiate the phot-hardening. Such alight source may be exemplified by low-, high- and ultrahigh-voltagemercury lumps, a xenon lump and an incandescent lamp and laser beams.The hardening of the resin may be conducted by exposing the entiresurfaces of the device after being applied with the resin, to light suchthat the resin is hardened simultaneously. Alternatively, thephoto-hardening may be effected in a step by step manner by scanning agathered spot light over the resin, for example, by moving a lightsource or using a photoconductive material such as an optical fiber Thismay be repeated more than tice.

According to the invention, an electrolyte or the precursor thereof isinjected into the cell through the openings provided in one of theelectrically conductive substrates forming the cell. Hereinafter, thedescriptions are made with respect to the electrolyte and the precursorthereof.

Although the electrolyte used for the electrochromic device produced bythe inventive method may be any type of electrolytes as long as they cancolor and bleach the electrochromic material contained in the device,preferred are those having an ion conductivity of more than 1×10⁻⁷ S/cmat room temperature. The electrolyte may be of liquid, gel or solid.Solid electrolytes are particularly preferred for the purpose of theinvention,

Eligible liquid electrolytes are those dissolving a supportingelectrolyte such as salts, acids and alkalis in a solvent. Any suitablesolvents may be used as long as they can dissolve the supportingelectrolyte. Particularly preferred are those having polarity. Specificexamples of such a solvent include water and organic polar solvents suchas methanol, ethanol, propylene carbonate, ethylene carbonate,dimethylsulfoxide, dimethoxyethane, acetonitrile, r-butyrolactone,r-valerolactone, sulforan, 1,3-dioxane, N,N-dimethylformamide1,2-dimethoxyethane and tetrahydrofuran Preferred are propylenecarbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane,acetonitrile, r-butyrolactone, sulforan, 1,3-dioxolane,N,N-dimethylformamide, 1,2-dimethoxyethane and tetrahydrofurun. Thesemay be used singular or in combination.

Although not restricted, salts used as the supporting electrolyte may bealkali metal salts, inorganic ion salts such as alkali earth metalsalts, quatemary ammonium salts and cyclic quaternary ammonium salts.Specific examples of such salts include alkali metal salts of lithium,sodium or potassium such as LiClO₄, LiSCN, LiBF₄. LiAsF₆, LiCF₃SO₃,LiPF₆, Lil, Nal, NaSCN, NaClO₄, NaBF₄, NaAsF₄, NaAsF₆, KSCN and KCl,quaternary ammonium salts or cyclic quaternary ammonium salts such as(CH₃)₄NBF₄, (C₂H₅)₄NBF₄, (n—C₄H₉)₄NBF₄, (C₂H₅)₄NBR, (C₂H₅)₄NClO₄ and(n—C₄H₉)₄NClO₄ and mixtures thereof.

Acids used as the supporting electrolyte may be exemplified by inorganicacids and organic acids which include sulfuric acid, hydrochloric acid,phosphoric acid, sulfonic acid carboxylic acid.

Alkalis used as the supporting electrolyte include sodium hydroxide,potassium hydroxide and lithium hydroxide.

The gelatinized-liquid electrolyte may be those which are gelatinized ormade to be viscous by adding a polymer or a gelatinizer to theabove-mentioned liquid electrolytes.

Preferred examples of such a polymer are polyacrylonitrile,carboxymethylcellulose, polyvinyl chloride, polyethylene oxide,polyurethane, polyacrylate, polyamide, polyacrylamide, cellulose,polyester, polypropyleneoxide and nafion.

Preferred examples of the gelafinizer are oxyethylenemethacrylate,oxyethyleneacrylate, urethaneacrylate, acrylamide and agar-agar.

The gelatinized-liquid electrolyte is sandwiched between the opposedelectrically conductive substrates by injecting into the cell themixture of h the precursor monomer of a polymer or the precursor of thegelatinizer and a liquid electrolyte then and then polymerizing orgelatinizing the mixture.

There is no particular limitation to the solid electrolyte if it issolid at room temperature and ion conductive. Preferred examples of suchsolid electrolyte are polyethyleneoxide, the polymer ofoxyethylenemethacrylate, nafion, polystyrene sulfonate, Li₃N, Na-β-Al₂O₂and In(HPO₄)₂H₂O. Particularly preferred are polymeric solidelectrolytes derived from polymerization of a polyethyleneoxide-basedcompound, an oxyalkyleneacrylate-based compound or aurethaneacrylate-based compound used as the main component of theprecursor.

A first example of such a polymeric solid elerolyte is one obtained bysolidifying a composition (hereinafter referred to as Composition A)which is used as a precursor and comprises an organic polar solvent, asupporting electrolyte and a urethaneacrylate represented by theformula.

wherein R¹ and R² may be the same or different and are each a group offormula (2), (3) or (4), R³ and R⁴ may be the same or different and areeach a C₁-C₁₂, preferably C₂-C₁₂ divalent hydrocarbon residue, Y isselected from a polyether unit, a polyester unit, a polycarbonate unitand the mixed unit thereof and n is an integer of 1-100.

wherein R⁵, R⁶ and R⁷ may be the same or different and are each ahydrogen atom or a C₁-C₃ alkyl group and R⁸ is a C₁-C₂₀, preferablyC₂-C₈ organic residue of divalent through quatervalent. Such organicresidues may be a hydrocarbon residue such as alkyltolyl,alkyltetratolyl and alkylene of the formula

wherein R⁹ is a C₁-C₃ alkyl group or hydrogen, p is an integer of 0-6and if p is greater than 2 the groups of R⁹ may be the same ordifferent.

The hydrocarbon residue may be a group part of which hydrogen atoms aresubstituted by an oxygen-containing hydrocarbon group such as a C₁-C₆,preferably C₁-C₃ alkoxy group and a C₆-C₁₂ aryloxy group. Specificexamples of group R⁸ in formulae (2) thorough (4) are those representedby the following

Each of the divalent hydrocarbon residues represented by R⁴ and R⁴ informula (1) is exemplified by a divalent chain-like hydrocarbon group,an aromatic hydrocarbon group and an alicydic-containing hydrocarbongroup. Specific examples of the chain-like divalent hydrocarbon groupare those represented by formulae (6) through (8)

wherein R¹⁰ and R¹¹ may be the same or different and are each aphenylene group, a phenylene group having an alkyl substituent, acycloalkylene group and a cycloalkylene group having an alkylsubstituent, R¹², R¹³, R¹⁴ and R¹⁵ may be the same or different and areeach a hydrogen atom or a C₁-C₃ alkyl group and q is an integer ofbetween 1 and 5.

Specific examples of the groups R³ and R⁴ in formula (1) are thoserepresented by the following formulae

CH₂CH₂CH₂CH₂CH₂CH₂

In formula (1), Y indicates a polyether unit, a polyester unit, apolycarbonate unit and mixed unit thereof. Each of these units isrepresented by the following formulae:

wherein R¹⁶ through R²¹ may be the same or different and are each aC₁-C₂₀, preferably C₂-C₁₂ divalent hydrocarbon residue, C₁-C₆ beingparticularly preferred for R¹⁹, m is an integer of 2-300, preferably10-200, r is an integer of 1-300, preferably 2-200, s is an integer of1-200, preferably 2-100, t is an integer of 1-200, preferably 2-100 andu is an integer of 1-300, preferably 10-200.

R¹⁶ through R²¹ are preferably straight or branched alkylene groupsamong which methylene, ethylene, trimethylene, tetramethylene,pentamethylene, hexamethylene and propylene groups are preferred forR¹⁶, and ethylene and propylene groups are preferred for R¹⁶, R¹⁷ andR¹⁹ through R²¹.

Each unit represented by formulae (a) through (d) may be a copolymer ofthe same or different units. In other words, if there exist a pluralityof the groups of each R¹⁶ through R²¹, the groups of each R¹⁶, R¹⁷, R¹⁸,R¹⁹, R²⁰ and R²¹may be the same or different. Preferred examples of suchcopolymers include a copolymer of ethylene oxide and a copolymer ofpropylene oxide.

In formula (1), n is preferably an integer of 1-50, more preferably1-20.

The urethaneacrylate of formula (1) has a molecular weight in the rangeof 2,500-30,000, preferably 3,000-20,000.

The urethaneacrylate has preferably 2-6, more preferably 2-4 functionalgroups per molecule.

The urethaneacrylate may be prepared by any suitable conventionalmethods.

There is no limitation to the organic polar solvent contained inComposition (A) as long as it has a polarity and can dissolve theelectrolyte. Preferred are propylene carbonate, ethylene carbonate,butylene carbonate, γ-butyrolactone, sulfolane, 1,3-dioxane,N,N-dimethylformamide, 1,2-dimethoxyethane, acetonitrile andtetrahydrofuran. These solvents may be used singular or in combination.The organic polar solvent is added in an amount of 100-1,200, preferably200-900 weight parts per 100 parts of the urethaneacrylate. Too lessamount of adding the organic polar solvent results in insufficient Ionconductivity, while too much amount causes a reduction in mechanicalstrength.

The supporting electrolyte contained in Composition (A) is selecteddepending on the usage of the device. Generally, the above-describedliquid electrolytes are preferably used. The supporting electrolyteshould be added in an amount of 0.1-30, preferably 1-20 weight percentof the organic polar solvent.

The first example of the solid polymeric electrolyte is essentiallyobtained by solidifying Composition (A) (precursor) composed of theurethaneacrylate, the organic polar solvent and the supportingelectrolyte If necessary, Composition (A) may be added with any suitablecomponents as long as they are not obstructive to the achievement of thepurpose of the invention. Such components may be crosslinkers and photo-and thermal-polymerization initiators tight or heat).

Composition (A) is injected through the opening of one of theelectrically conductive substrates disposed, facing each other to from acell and then is cured in a conventional manner such that the firstexample of the solid polymeric electrolyte is sandwiched between theelectrically conductive substrates. The term “curing” used hereindesignates a state where the component is cured with the progress ofpolymerization (polycondensation) or crosslinking and thus thecomposition does not flow at room temperature. The urethaneacrylate hasthe basic structure in the form of network by curing.

A second example of the polymeric solid electrolyte is obtained bysolidifying a composition (hereinafter refereed to as Composition (B))which is used as a precursor and comprising an organic polar solvent, asupporting electrolyte, a monofunctional acryloyl-modified polyalkyleneoxide and/or a polyfunctional acryloyl-modified polyalkylene oxide.

Ad the mono-functional acryloyl-modified polyalkylene oxide isrepresented by the formula

wherein R²², R²³, R²⁴ and R²⁵ may be the same or different and are eachhydrogen and an alkyl group having 1-5 carbon atoms and n is an integerof greater than 1.

Specific examples of such alkyl group Include methyl, ethyl, i-propyl,n-propyl, n-butyl, t-butyl and n-pentyl. Preferred for R²², R²³ and R²⁴are hydrogen and a methyl group. Preferred for R²⁵ are hydrogen, amethyl and ethyl group.

n in formula (16) is an integer greater than 1, usually between 1 and100, preferably 2 and 50, more preferably 2 and 30.

Specific examples of compounds represented by formula (16) are thosehaving 1-100, preferably 2-50, more preferably 1-20 oxyalkylene units,such as methoxypolyethylene glycol methacrylate, methoxpolypropyleneglycol methacrylate, ethoxypolyethylene glycol methacrylate,ethoxypolypropylene glycol methacrylate, methoxypolyethylene glycolacrylate, methoxypolypropylene glycol acrylate, ethoxypolyethyleneglycol acrylate, ethoxypolypropylene glycol acrylate and mixturesthereof.

If n is greater than 2, the compound may be those having differentoxyalkylene units, that is, copolymerized oxyalkylene units which forinstance have 1-50, preferably 1-20 oxyethylene units and 1-50,preferably 1-20 oxypropylene units Specific examples of such compoundsare (ethylene propylene) glycol methacrylate, ethoxypoly(ethylene-propylene) glycol methacrylate, methoxypoly (ethylenepropylene) glycol methacrylate, methoxypoly (ethylene-propylene) glycolacrylate, ethoxypoly methoxypoly (ethylene propylene) glycol acrylateand mixtures thereof.

Eligible polyfunctional acryloyl-modified polyalkylene oxide forComposition (B) is a bifunctional acryloyl-modified polyalkylene oxideor a polyfunctional acryloyl-modified polyalkylene oxide having morethan three functional groups. The bifunctional acryloyl-modifiedpolyalkylene oxide is represented by the formula

wherein R²⁶, R²⁷, R²⁸ and R²⁹ are each hydrogen and a C_(1-C) ₅ alkylgroup and m is an integer greater than 1. The polyfunctionalacryloyl-modified polyalkylene oxide having more than three functionalgroups is represented by the formula

wherein R³⁰, R³¹ and R³² are each hydrogen and a C₁-C₆ alkyl group, p isan integer greater than 1, q is an integer of 2-4 and L is a connectinggroup of valence indicated by q.

If R²⁶, R²⁷, R²⁸ and R²⁹ are alkyl groups, such alkyl groups may bemethyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl, t-butyl andn-pentyl. Preferred for R²⁶, R²⁷, R²⁸ and R²⁹ are hydrogen and a methylgroup.

m in formula (17) is an integer greater than 1, usually 1-100,preferably 2-50, more preferably 2-30 Preferred examples of compounds offormula (17) are those having 1100, preferably 2-50, more preferably1-20 oxyalkylene units such as polyethylene glycol diacrylate,polypropylene glycol dimethacrylate, polyethylene glycol diacrylate,polypropylene glycol dimethacrylate and mixtures thereof.

If m is greater than 2, the compounds of formula (17) may be thosehaving different oxyalkylene units, that is, polymerized oxyalkyleneunit having 1-50, preferably 1-20 oxyethylene units and 1-50, preferably1-20 oxypropylene units, such as poly(ethylene propylene)glycoldimethacrylate, poly(ethylene-propylene) glycol diacrylate and mixturesthereof.

If R³⁰, R³¹ and R³² are alkyl groups, preferred are methyl, ethyl,i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl groups. Particularlypreferred for R³⁰, R³¹ and R³² are hydrogen and a methyl group.

p in formula (18) is an integer of usually between 1 and 100, preferably2 and 50, more preferably 2 and 30.

q in formula (18) is a number of connecting group “L” and an integerbetween 2 and 4.

Connecting group “L” is a divalent, trivalent or quatervalenthydrocarbon group having 1-30, preferably 1-20 carbon atoms.

Such divalent hydrocarbon groups may be alkylene, arylene, arylalkylene,alkylarylene and hydrocarbon groups having those groups as the baseskeleton. Specific examples of such hydrocarbon groups are thoserepresented by the following formulae:

Such trivalent hydrocarbons groups may be alkyltryl, aryltryl,arylalkyltryl, alkylaryltryl and hydrocarbon groups having those groupsas the base skeleton. Specific examples of such hydrocarbon groups arethose represented by the following formulae:

The quatervalent hydrocarbon group may be alkyltetraryl, aryltetraryl,arylalkyltetraryl, alkylaryltetraryl or hydrocarbon groups having thosegroups as the base skeleton. Specific examples are those represented bythe following

Specific examples of compounds of formula (18) are those having 1-100,preferably 2-50, more preferably 1-20 of an oxyalkylene units such as

trimethylolpropanetri(polyethylene glycol acrylate),

trimethylolpropanetri(polyethylene glycol methacrylate),

trimethylolpropanetri(polypropylene glycol acrylate),

trimethylolpropanetri(polypropylene glycol methacrylate),

tetramethylolmethanetetra(polyethylene glycol acrylate),

tetramethylolmethanetetra(polyethylene glycol methacrylate)

tetramethylolmethanetetra(polypropylene glycol acrylate)

tetramethylolmethanetetra(polypropylene glycol methacrylate),

2,2-bis[4-(acryloxypolyethoxy)phenyl]propane,

2,2-bis[4-(methaacryloxypolyethoxy)phenyl]propane,

2,2-bis[4-(acryloxypolylsopropoxy)enylyl]propane,

2,2-bis[4-(methaacryloxypolyisopropoxy)phenyl]propane and mixturesthereof

If p is more than 2, compounds of formula (18) may be those havingdifferent oxyalkylene units, that is, polymerized oxyalkylene unitshaving 1-50, preferably 1-20 of oxyethylene units and 1-50, preferably1-20 oxypropylene units. Specific examples of such compounds include

trimethylolpropanetri(poly(ethylene-propylene)glycol acrylate),

trimethylolpropanetri(poly(ethylene-propylene)glycol methacrylate),

tetramethylolmethanetetra(poly(ethylen-propylene)glycol acrylate),

tetramethylolmethanetetra(poly(ethylene-propylene)glycol methaacrylate)and

mixtures thereof.

Needless to mention, there may be used the difunctionalacryloyl-modified polyalkyleneoxide of formula (17) and thepolyfunctional acryloyl-modified polyalkyleneoxide of formula (18) incombination. When these compounds are used in combination, the weightratio of the compound of formula (17) to that of formula (18) Is in therange between 001/99.9 and 99.9/0.01, preferably 1/99 and 99/1, morepreferably 20/80 and 80/20. When the compound of formula (16) is used incombination with the compound of formula (17) or (18), the weight ratiotherebetween is in the range of usually between 1/0.001 and 1/1,preferably 1/0.06 and 1/0.5.

The organic polar solvent and supporting electrolyte described wathrespect to Composition (A) are also eligible for Composition (B). Theorganic polar solvent should be added in an amount of 50-800, preferably100-500 weight percent based on the total weight of the monofunctionalacryloyl-modified polyalkyleneoxide and the polyfunctionalacryloyl-modified polyalkyleneoxide.

The supporting electrolyte should be added in an amount of 1-30,preferably 3-20 weight percent based on the total weight of themonofunctional acryloyl-modified polyalkyleneoxide and thepolyfunctional acryloyl-modified polyalkyleneoxide.

If necessary, Composition (B) may be added with another componentsoptionally as long as they do not bother the achievement of the purposeof the invention. Such components may be photopolymerization initiatorsor thermal polymerization initiators. These initiators should be addedin an amount of 0.05-5, preferably 0.01-3 weight percent based on thetotal weight of the monofunctional acryloyl-modified polyalkyleneoxideand the polyfunctional acryloyl-modified polyalkyleneoxide.

Composition (B) is injected through the opening of one of theelectrically conductive substrates disposed, facing each other to from acell and then is cured in a conventional manner so that the secondexample of the solid polymeric electrolyte Is sandwiched between theelectrically conductive substrates. The term “curing” used hereindesignates a state where the monofunctional acryloyl-modifiedpolyalkyleneoxide or the polyfunctional acryloyl-modifiedpolyalkyleneoxide is cured with the progress of polymerization(polycondensation) or crosslinking and thus the composition does notflow at room temperature. In this case, the monofunctionalacryloyl-modified polyalkyleneoxide or the polyfunctionalacryloyl-modified polyalkyleneoxide has the basic structure in the formof network.

According to the invention, any of the abovedescribed liquid,gelatinized and solid electrolytes is generally injected into the cell.However, needless to mention, an electrolyte other than theabove-described electrolytes may be injected into the cell. Thegelatinized- and solid- electrolytes are injected into the cell in theform of a precursor. As already described, the electrolyte or theprecursor may be added with the electrochromic material beforehand. Uponthe injection, there is selected a suitable method which can fill evenlythe space between the two electrically conductive substrates with theelectrolyte or the precursor. There is usually employed a vacuuminjection method in which the hollow interior of the cell is evacuatedso as to be ideally in vacuum and then the injection port opening of thecell is submerged into the liquid electrolyte or the precursor underatmospheric pressure such that the liquid electrolyte is supplied intothe cell by utilizing the difference in pressure between the outside andinside of the cell.

Upon completion of the injection, before the precursor is gelatinized orsolidified, the injection port opening of the cell is temporarily closedor sealed with a material which can be deformably inserted into theinjection port. Eligible materials for this temporarily sealing arethose which are resilient and resistant against the electrolyte or theprecursor thereof. Typical examples of such materials are a naturalrubber and a synthetic rubber such as isoprene rubber, butadiene rubber,styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber,chloroprene rubber, chlorosulfonated polyethylene, nitrile rubber,urethane rubber, polysulfide rubber, acrylic rubber, epichlorohydrinrubber, silicone rubber, fluorine rubber, hydrogenated nitrile rubberand the like.

After the temporarily sealing, the electrolyte or the precursor thereofadhered around the injection port is then removed by washing andthereafter the temporarily sealed injection port is secondarily sealedwith an adhesive. Such an adhesive for sealing secondarily the injectionport may be selected from various types of adhesives such as those ofphoto-, thermal-, room temperature and electro beam-setting types. As amatter of course, there may be used acrylic-, epoxy- and silicone-resinadhesives as well as other types of adhesives such as phenolic resin,urea resin, epoxy resin, polyvinyl acetate, polyvinyl acetal, polyvinylalcohol, acrylic and methacrylic esters, cyanoacrylate and polyamide.These may be used singular or in combination. Alternatively, these maybe modified or added with fillers.

In view of solvent resistance, the epoxy resin is found to beparticularly superior. An acrylic-modified epoxy resin of photo-settingtype is preferred. Preferred for such an acrylic-modified epoxy resinare those having 0.01-0.3 mol, preferably 0.05-0.2 mol of acrylicresidue per mol of epoxy residue

Thermo setting of the adhesive for bonding the sealing member to thecell may be conducted by using various types of heat source such asovens, infrared heaters, electric heaters and surface type heatgenerators at a temperature ranging from room temperature to 150° C.,preferably room temperature to 100° C. The time required for thethermo-setting is not restricted but is usually within 24 hours,preferably within one hour.

The photo-setting may be conducted by using various types of lightsources such as low-, high- and ultrahigh-voltage mercury vapor lamps, axenon lamp, an Incandescent lamp and laser beams. The photo-setting ofthe adhesive may be conducted by exposing evenly the entire surfaces ofthe device to light after being applied with the adhesive.Alternatively, a step by step manner may be employed which is effectedby scanning a gathered spot light over the device, for example, bymoving a lump or a light source or using a photoconductive material suchas an optical fiber or a mirror. Practically preferred are methods usinga 100 W-1 KW ultrahigh voltage mercury vapor lamp or a xenon-mercuryvapor lamp. Among those methods, preferred are methods which guide thelight from a light source of a 200 W-500 W xenon-mercury vapor lampusing an optical fiber.

The secondary sealing of the present invention includes a method inwhich a sheet-like member is applied to the injecting port with anadhesive thereby increasing the durability of the sealing portion of theinjection port. Eligible for this sheet-like member are any type ofmaterials which can be bonded with an adhesive. Such materials are aglass sheet, a ceramic sheet and a synthetic resin sheet such aspolyester, polyethylene terephtalate, polyamide, polysulfone, polyethersulfone, polyether otherketone, polyphenylene sulfide, polycarbonate,polyimide, polymethyl methacrylate, polystyrene, tricellulose acetate,polymethylpentene, polysiloxane, polyethylene, polypropylene,polycellulose acetate, phenolic resin, urea resin, epoxy resin,polyvinyl acetate, polyvinyl acetal, polyvinyl alcohol, acrylic andmethacrylic esters and cyanoacrylate.

According to the invention, since after the injection of the electrolyteor the precursor thereof the resilient sealing member closing theinjection port of the cell can isolate the electrolyte or the precursorthereof injected thereinto from the influence of the outside of thecell, the complete removal of the electrolyte or the precursor thereofadhered around the injection port can be achieved merely by washing,resulting in that the adhesive for bonding the sealing member to thecell is free from the hindrance in adhesive capability caused by beingmixed with the electrolyte or the precursor thereof. Furthermore, due tothe injection port provided in the electrically conductive substrate,the inventive method, even upon the production of large size ofelectrochromic devices, is not only free from the risk that the sealingmember comes out from the cell by the deformation thereof caused bystress and but also is contributive to enhance the durability of thesealing member because the sealing member is firmly fixed to thesubstrate by bonding with the adhesive.

The present invention will now be explained in further detail withreference to Examples, which are given only by way of illustration, butare not intended for limiting the invention.

EXAMPLE 1 Preparation of Counterelectrade for Electrochromic Device

A pasty active carbon was prepared by mixing 80 g of active carbonpowder manufactured by KURARE under the trade name of YR17, 40 g ofgraphite manufactured by NIPPON KOKUEN SHOJI CO., LTD under the tradename of USSP, 343 g of a silicone resin manufactured by NIPPON UNICARCO., LTD. under the trade name of RZ7703 and 25 g of butyl cellosolve.On an ITO glass substrate (a transparent electrically conductive glassproduced by forming a layer having a thickness of 2,500 Å on a glasssubstrate by sputtering using an In₂O₃:Sn target of 10 Ω/sq inelectrical surface resistance, 2 mm in thickness and 50cm×50 cm in size,the above-obtained active carbon paste was screen-printed to form astriped pattern; each stripe is 500 μm in width and 100 μm in height.The printed area was 20% of the total area of the electrode layer. Theprinted active carbon was cured by heating at a temperature of 180° C.for 90 minutes thereby obtaining a counterelectrode.

Preparation of Electrochromic Electrode for Eletrochromic Device

On an ITO glass substrate which has an 4mm φ opening located 15 mm apartfrom the sides of the substrate, of 10 Ω/sq in electrical surfaceresistance, 2 mm in thickness and 50 cm×50 cm in size, a 500 Å thicktungsten oxide film was deposited at room temperature under thecondition of 10-30 Å/second to obtain an electrochromic electrode.

The counterelectrode substrate and the electrochromic electrodesubstrate were placed in a 500 μm spaced apart opposing relationship,followed by sealing the peripheral edges of the opposed substratesthereby producing a hollow cell. A butyl rubber of 5 mm wide had beenapplied to the peripheral edges as a primary sealant and athermo-setting epoxy resin sealant of 5mm wide as a secondary sealant.The sealants were cured at 90° C. for one hour.

An electrolyte solution (1 mol/L concentration) containing a supportingelectrolyte of LiClO₄ in γ-butyrolactone solvent was deaerated and theninjected through the opening into the hollow cell in vacuum. Uponcompletion of the charging of the electrolyte, the opening wastemporarily sealed by inserting thereinto a butyl rubber. After theremoval of the electrolyte adhered on the cell surface around the butylrubber by washing with an ethanol, the opening was coated with aphoto-setting adhesive manufactured by THREE BOND under the trade nameof 3025 and then applied to a light of 4,000 mJ by a high voltagemercury vapor lamp such that the adhesive is cured and the secondarysealing was completed, thereby obtaining an electrochromic device.

The coloring and bleaching test was carried out to measure the change ofoptical density. First, an electrical voltage of 1.5 V was appliedacross the electrochromic device for 150 seconds so as to be negative atthe electrochromic electrode with respect to the counterelectrode. Theelectrochromic device was uniformly colored in blue, and the change inoptical density at the center of me device was 0.50.

Immediately after the 150-second coloration of the device, an electricalvoltage of 1.0 V was in turn applied across the device for 60 seconds soas to be positive at the electrochromic electrode against thecounterelectrode. The device was then bleached back to the colorlessinitial state.

The electrochromic device was left in an oven at 65° C. and a humidityof 95% for 1,000 hours. The device was taken out from the oven and thepeel off at the sealing portion was not observed.

The electrochromic device was placed on 5 cm³ of acrylic supportingmembers situated under the comers of the device so as to be deformed byits weight for one month. The peel off at the sealing portion was notobserved.

Coloring and Bleaching Test

633 nm of He—Ne laser beam expanded in diameter to 20 mm by a beamexpander was Irradiated so as to pass through the center of theelectrochromic device and the transmitted light was measured by using anSi photodiode. On applying an electrical voltage for coloration, thetransmitted light intensity was measured every 5 seconds, If thetransmitted light volume in t second after the coloration voltage isapplied is expressed by T(t), the change in optical density is definedby the following equation:

Change in Optical Density=log[T Bleach/T(t)](log is common logarithms)

EXAMPLE 2

An electrochromic device was produced by following the procedures ofExample 1 except that after a photo-setting adhesive manufactured byTHREE BOND under the trade name of 3025 had been applied on theinJection opening, a glass sheet of 3 cm×3 cm in size was place over theadhesive and then exposed to a light of 4,000 mJ by a high voltagemercury vapor lamp thereby completing the secondary sealing.

The coloring and bleaching test was carried out to measure the change ofoptical density. First, an electrical voltage of 1.5 V was appliedacross the electrochromic device for 150 seconds so as to be negative atthe electrochromic electrode with respect to the countereledrode. Theelectrochromic device was uniformly colored in blue, and the change inoptical density at the center of the device was 0.50.

Immediately after the 150-second coloration of the device, an electricalvoltage of 1.0 V was in turn applied across the device for 60 seconds soas to be positive at the electrochromic electrode against thecounterelectrode. The device was then bleached back to the colorlessinitial state.

The electrochromic device was left in an oven at 65° C. and a humidityof 95% for 1,000 hours. The device was taken out from the oven and thepeel off at the sealing portion was not observed.

The electrochromic device was placed on 5 cm³ of acrylic supportingmembers situated under the comers of the device so as to be deformed byits weight for one month. The peel off at the sealing portion was notobserved.

EXAMPLE 3

A photo-setting type electrolyte solution was prepared by admixing 20weight percent of methoxytetraethylene glycol methacrylate and 0.02weight percent of DAROCURE 1173 to an electrolyte solution (1 mol/L)containing an LiClO₄ electrolyte in a solvent of γ-butyrolactone.

The procedures of charging the electrolyte and sealing the opening(charging port) of Example 1 were followed except for using theabove-obtained electrolyte. After completion of the secondary sealing ofthe opening with use of a photo-setting type adhesive, the electrolytein the cell was cured by a light of 20 J in illumination from a highvoltage mercury vapor lamp thereby providing an electrochromic device.

The coloring and bleaching test was carried out to measure the change ofoptical density. First, an electrical voltage of 1.5 V was appliedacross the electrochromic device for 150 seconds so as to be negative atthe electrochromic electrode with respect to the counterelectrode. Theelectrochromic device was uniformly colored in blue, and the change inoptical density at the center of the device was 0.48.

Immediately after the 150-second coloration of the device, an electricalvoltage of 1.0 V was in turn applied across the device for 60 seconds soas to be positive at the electrochromic electrode against thecounterelectrode. The device was then bleached back to the colorlessinitial state.

The electrochromic device was left in an oven at 65° C. and a humidityof 95% for 1,000 hours. The device was taken out from the oven and thepeel off at the sealing portion was not observed.

EXAMPLE 4

A cell was prepared by following the procedures of Example 1 except thatthe space between the substrates was changed to 200 μm. Anelectrochromic device was prepared by charging the electrolyte ofExample 1 in vacuum into the cell and following the rest of theprocedures of Example 1.

The coloring and bleaching test was carried out to measure the change ofoptical density. First, an electrical voltage of 1.5 V was appliedacross the electrochromic device for 150 seconds so as to be negative atthe electrochromic electrode with respect to the counterelectrode. Theelectrochromic device was uniformly colored in blue, and the change inoptical density at the center of the device was 0.50.

Immediately after the 150-second coloration of the device, an electricalvoltage of 1.0 V was in turn applied across the device for 60 seconds soas to be positive at the electrochromic electrode against thecounterelectrode. The device was then bleached back to the colorlessinitial state.

The electrochromic device was left in an oven at 65° C. and a humidityof 95% for 1,000 hours. The device is taken out from the oven and thepeel off at the sealing portion was not observed.

COMPARATIVE EXAMPLE 1

A cell of the same in size as that produced in Example 1 was produced.Instead of making an opening in the surface of the substrate, this cellhas an opening of 10 mm width made by omitting a part of sealing appliedto the peripheral edge of the two opposing substrates.

An electrolyte solution (1 mol/L concentration) containing anelectrolyte of LiClO₄, In γ-butyrolactone solvent was charged in vacuuminto the above-obtained cell, After washing the charging port with anethanol, it was coated with a photo-setting adhesive manufactured byTHREE BOND under the trade name of 3025 and then exposed to a light of4,000 mJ in illumination from a high voltage mercury vapor lamp therebysealing the port.

The electrochromic device was left in an oven at 66° C. and a humidityof 95% for 400 hours. The device is taken out from the oven and the peeloff was observed at the sealing portion of the port.

COMPARATIVE EXAMPLE 2

An electrochromic device produced by following the procedures ofComparative Example 1 was placed on 5 cm³ of acrylic supporting memberssituated under the comers of the device so as to be deformed by itsweight for one week. The peel off was observed at the portion of thesealing for the port.

What is claimed is:
 1. A method for producing an electrochromic devicewhich comprises the steps of (a) assembling a hollow cell constitutingan electrochromic device by opposing two electrically conductivesubstrates, at least one of which is transparent and either of which isprovided with an injection port for an electrolyte or a precursorthereof, in a spaced-apart relationship with each other and sealingtogether the entire peripheral edges of the opposed substrates; (b)filling the inside of the hollow cell with an electrolyte or theprecursor thereof by injecting through the injection port; (c) sealingtemporarily the injection port with a material selected from the groupconsisting of a natural rubber and a synthetic rubber which isdeformably inserted into the port; and (d) sealing secondarily thetemporarily sealed port by applying thereon only an adhesive or a sheetmember over the adhesive.
 2. A method for producing an electrochromicdevice according to claim 1 wherein said synthetic rubber is selectedfrom the group consisting of isoprene rubber, butadiene rubber,styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber,chloroprene rubber, chlorosulfonated polyethylene, nitrile rubber,urethane rubber, polysulfide rubber, acrylic rubber, epichlorohydrinrubber, silicone rubber, fluorine rubber and hydrogenated nitrilerubber.
 3. A method for producing an electrochromic device according toclaim 1, wherein the secondary sealing is carried out by applying thesheet member over the adhesive on the temporarily sealed port, and saidsheet member is selected from the group consisting of a glass sheet, aceramic sheet and a synthetic resin sheet.
 4. A method for producing anelectrochromic device according to claim 3 wherein said sheet member isa synthetic resin sheet and said synthetic resin sheet is formed from amaterial selected from the group consisting of polyethyleneterephtalate, polyamide, polysulfone, polyether sulfone, polyetheretherketone, polyphenylene sulfide, polycarbonate, polyimide, polymethylmethacrylate, polystyrene, tricellulose acetate, polymethylpentene,polysiloxane, polyethylene, polypropylene, polycellulose acetate,phenolic resin, urea resin, epoxy resin, polyvinyl acetate, polyvinylacetal, polyvinyl alcohol, acrylic and methacrylic esters andcyanoacrylate.